No such rule, but you are generally judged on impact and not effort at Google. If your efforts don't make an impact, then they aren't going to be counted in your favor.

Isn't that how the world works? Effort without impact is just wasted effort.

The real world, yes. In many institutions (eg. the public school system, most giant megacorps) you get points for showing up and putting in the appearance of effort even if you don't accomplish anything.